FIELD OF THE INVENTION
The invention relates generally to geometric modeling systems that, with the aid of a digital computer, may be used to capture, manipulate, analyze and report data. Examples of such systems include geographical positioning systems (GPS), geographic information systems (GIS), computer aided design (CAD) systems and computer aided manufacturing (CAM) systems.
More particularly, the invention relates to methods and apparatus used in geometric modeling systems for visibly distinguishing areas (images) on a display screen generated from raster data from areas on the same screen generated from vector data. An example of where the invention may be applied is in graphical systems in which geographic information is displayed with the graphic data being made up of both vector data (such as a set of points defining a road input to the system by the user via a digitizing tablet) and raster data (such as a photo image of the same road that is digitized via a scanner).
According to the invention, the brightness of each data type (vector or raster) image being displayed may be modified by the user. In one embodiment of the invention, in response to user interaction with the system, the brightness of the raster data, the vector data, or both (and hence their images once displayed), may be modified by adjusting entries in color tables (or specific entries of a single color table) maintained for each data type.
By changing color specification entries in each color table (or the color specification of assigned data type entries within a single color table), the vector and raster data that is subsequently output to a display can be distinguished based on the shift in brightness of the image appearing on the screen in response to the aforementioned user action.
The invention is particularly useful in situations where, in an exemplary application, raster data may assume any color in a defined color spectrum; making vector data and raster data indistinguishable by, for example, reassignment of color designations.
The invention may also be used in computer graphic systems which are not geometric modeling systems per se, to generally support graphics processing functions.